1. Technical Field
The present invention relates to liquid ejecting heads and liquid ejecting apparatuses.
2. Related Art
Ink jet recording heads have a problem such that when air bubbles residing in ink are supplied to a head body, the air bubbles can cause an ink discharge defect such as a dot missing. In order to solve such problem, an ink jet recording head in which a filter is disposed in an ink passage is proposed by JP-A-11-10904, for example. The filter in the ink passage removes air bubbles in the ink so as to prevent the air bubbles from flowing into the head body.
Meanwhile, as an ink jet recording head that discharges a high-viscosity ink, JP-A-06-143602 discloses an ink jet recording head that is configured such that ink which has not been discharged from nozzles is circulated through an external tank or the like and is supplied again to an ink passage from the external tank. Further, as a head body of an ink jet recording head, there is known a head body that includes a lead-out passage from which the ink, which has been supplied from an upstream passage and passed through a filter, is supplied to nozzles and also includes a downstream passage which circulates the ink, which has not passed through the filter, to the tank.
In an ink jet recording head equipped with such head body, a filter is arranged in parallel to a passage in which ink flows toward the tank without passing through the filter. As a result, an area of the filter to trap foreign objects becomes larger without making the size of a passage forming member be large in a width direction thereof. This makes it possible to suppress a pressure loss and surely trap the foreign objects.
However, it actually takes place even in the ink jet recording head equipped with the above-mentioned head body that air bubbles flow into the ink passage and block the passage to cause unfavorable effects on ink discharge. To be more specific, in order to suppress a pressure loss, and the like, the filter is arranged in parallel to the ink passage in which the ink that does not pass through the filter flows toward the tank. As a result, it is difficult to provide a method for removing the air bubbles in such configuration. Therefore, a requirement for a technique to remove the air bubbles has been greatly increased these days.